TuMV Brassicas

This invention relates to virus-resistant plants and to methods of generating such plants. This invention extends to eukaryotic translation initiation factor variants and isoforms thereof, and to nucleic acids involved in the splicing of such variant factors, and uses thereof in methods for producing plants that are resistant to viral infections. The identification of the trait is supported using molecular markers.

Viruses present a significant problem in agriculture. For example, plant viruses in the family Potyviridae (potyviruses) represent approximately 30% of plant viruses and are capable of infecting more than 30 different families of plants, leading to extensive crop damage and even death. In particular, the Solanaceae, Cucurbitaceae and Fabaceae plant families are especially sensitive to infection by potyviruses. Currently, in contrast to many bacterial or fungal infections, there are few ways to combat viral infections in plants. Due to the increasing size of the international market for plants and seeds, it is becoming more essential for plant breeders to develop plants that are resistant to infection from viruses, for example those from the Potyviridae family.

Upon infection of a plant host, plant viruses use some of the host's endogenous proteins to complete their own life cycle. For example, potyviruses, such as Turnip mosaic virus (TuMV), use plant eukaryotic translation initiation factors to bind plant ribosomes to the viral genomic RNA as a pre-requisite to translating their genomes into various viral proteins, including the viral RNA-dependent RNA polymerase that is essential to produce more copies of the virus. Therefore, defects in the plant eukaryotic translation initiation factors may confer viral resistance in plants. However, since the eukaryotic translation initiation factors are vital to the survival of plants, defects in the eukaryotic translation initiation factors are detrimental to plants, often resulting in plants that are non-viable.

It was discovered that using multiple copies of eukaryotic translation initiation factors in Brassica rapa facilitate a broad-spectrum virus resistance. Recessive strain-specific resistance to a number of plant viruses in the Potyvirus genus has been found to be based on mutations in the eukaryotic translation initiation factor 4E (eIF4E) and its isoform, eIF(iso)4E. We identified three copies of eIF(iso)4E in a number of Brassica rapa lines.

The existence of multiple copies has enabled redundancy in the host plant's translational machinery, resulting in diversification and emergence of the resistance. Deployment of the resistance is complicated by the presence of multiple copies of the gene.

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